This invention relates to a catheter for controllably obstructing blood flow in a vein and more particularly to such a catheter having ports on either side of the obstruction for measuring the differential pressure therebetween as a measure of the degree of obstruction obtained.
When surgery is performed on a patient in a supine (horizontal) position, air embolism is not possible because pressure within the veins is greater than atmospheric pressure. For the supine patient, open veins bleed. However, when the patient is positioned in the sitting upright position, the pressure in veins of the neck and head becomes negative in relation to atmospheric pressure, and those veins, if cut, readily draw in air.
Surgery in the upright position is a highly desirable condition sought by surgeons for certain types of operation including brain surgery, but the high probability of air inspiration into cut veins discourages and curtails this practice. Air embolism is a dreadful, insidious condition which may totally overshadow gains obtained by performing surgery in the sitting position. Air embolism can successfully be detected, but treatment, while surgery is in progress can be a nightmare. Air embolism produces a frothy blood mixture which is difficult to aspirate and attempts of air removal are often fruitless, too late and disastrous.
There is thus a long felt need for a solution to this problem.
It is therefore the object of this invention to provide a method for preventing air aspiration into cut veins and consequent air embolism during surgery of the neck and head of a patient in the sitting position.
It is a further object of this invention to provide a catheter insertable into the patient's vena cava that includes a means for controllable partial blockage of the vena cava and a means for measuring the differential blood pressure on either side of the blockage to guide blockage control.